<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>JS变量_typeof</title>

    <script>
      var num1 = 1;


      //定义 number 类型
      var num1 = 1;
      var num2 = 1.2;
      var num3 = NaN;

      //输出到页面上
      document.write(num1+"---"+typeof(num1)+"<br>");
      document.write(num2+"---"+typeof(num2)+"<br>");
      document.write(num3+"---"+typeof(num3)+"<br>");

      //定义 string 类型
      var str = "abc";
      var str2 = 'edf';

      document.write(str+"---"+typeof(str)+"<br>");
      document.write(str2+"---"+typeof(str2)+"<br>");

      //定义 boolean
      var flag = true;
      document.write(flag+"---"+typeof(flag)+"<br>");

      //定义 null
      var obj = null;
      var obj2 = undefined;
      var obj3;
      document.write(obj+"---"+typeof(obj)+"<br>");
      document.write(obj2+"---"+typeof(obj2)+"<br>");
      document.write(obj3+"---"+typeof(obj3)+"<br>");

    </script>
</head>
<body>

</body>
</html>